1. Field of the Invention
The present invention relates to an information search system which promptly searches for user's desired information.
2. Description of the Related Art
Along with penetration of the Internet into the society, the quantities of information that people handle in daily life and social activities become huge. Also, the quantities of information are increasing drastically on a daily basis in the present state. The spread of communication networks enhances the convenience to browse worldwide information. Web services, EDI (electronic data interchange), EC (electronic commerce), and the like become everyday affairs.
Furthermore, by the improved infrastructures and enhanced transmission qualities of high-speed optical communication Internet networks, terrestrial digital broadcasting, satellite communication networks, and GPS (global positioning system), one can use networks regardless of location across the globe. The human society receives the benefits of availability of high-value-added information everywhere using the spread of these information networks and inexpensive devices.
However, it becomes difficult for the people to promptly and adequately search for required desired information from information in huge quantities. Since the quantities of information are too much, and they are located everywhere, an advanced technique is required for a search method.
Enterprises, companies, and individuals require a wide variety of information. It is demanded to instantly provide specialized information as well as corporate information, academic information, and general information.
A search from a gene sequence information database and a full-text search from a literature database are required to handle Terabyte-class information.
In recent years, operation logs of computers are often acquired and stored on a daily basis in enterprises so as to grasp whether or not computers are appropriately used. Such operation logs are stored daily and the quantities of information (data) often reach Terabytes.
In order to use such information, it is required to promptly search information in large quantities for desired information. However, it is difficult for versatile, commercially available relational databases to handle Terabyte-class information.
Information which is difficult for a commercially available database to handle is normally saved in a structured information format such as an XML (extensible markup language) or CSV (comma separated values: a file format that enumerates information by separating it for respective items by commas) format, or a unique format.
As a device for handling structured information, the following proposal such as “XML CSV compression” is known (see patent references 1 and 2). With this proposal, for example, elements other than elements to be processed in XML documents are expressed using a CSV format with respect to XML data so as to reduce the load on a CPU (central processor unit) and to attain memory savings.
Normally, in order to search a large-capacity database for desired information, the user often narrows down conditions step by step and repeats such processes by trial and error.
However, upon searching large-capacity information, a long time is required per information search. Hence, such trial and error works cannot be done within a predetermined period of time (e.g., several hours), and it is normally difficult to practically obtain desired information.
Especially, in case of such large-capacity information, since a time required for file read/write processes with disk I/O (Input/Output) accesses is not negligible, it is important to reduce the number of read/write times of files throughout a user's work, so as to enhance the efficiency and to shorten a time for the user's work.    Patent Reference 1: Jpn. Pat. Appln. KOKAI Publication No. 2006-277031    Patent Reference 2: Jpn. Pat. Appln. KOKAI Publication No. 2007-179492